This invention relates to a pushbutton tuner, and more particularly to what is called a 5-10 pushbutton tuner. A 5-10 pushbutton tuner means a tuner wherein five pushbuttons are, in one mode of operation, used for selecting AM broadcast stations and, in another mode of operation, used for selecting FM broadcast stations, it being possible, with five pushbuttons, to select the maximum five different AM broadcasts and the maximum five different FM broadcasts.
This type of tuner is disclosed and claimed in, for example, Newman U.S. Pat. No. 3,357,264 (Re. 27,179) and Stamm U.S. Pat. No. 3,415,129.
Generally, this type of device has slide actuating members with pushbuttons mounted thereto respectively and which slide in response to the push-in of the respective pushbuttons. Each of said actuating members is provided on both sides thereof with follow-up members either of which can be selectively engaged with the actuating member to slide with the sliding thereof. The follow-up member has a frequency defining cam mounted thereto, which, upon sliding with the actuating member, sets the tuning mechanism to a frequency to be determined depending upon the setting state of said cam. If five actuating members are provided, then a total of ten follow-up members are to be provided, of which five, for example, on the right sides of the actuating members are associated with the tuning mechanism so as to cause it to carry out tuning in one band (AM or FM broadcasts), and the five follow-up members on the left sides of the actuating members are associated with the same tuning mechanism so as to cause it to carry out tuning in another band (FM or AM broadcasts). Means is provided for manually engaging the actuating members with the follow-up members for tuning in each band. This broadcast band manual selecting means engages all of the actuating members with the respective follow-up members on the right side or the left side in accordance with a broadcast band to be selected.
In the Newman patent, this broadcast band manual selecting means comprises a toggle lever articulately mounted on the upper part of each actuating member and a slidable gate which manually selectively engages all of the toggle levers with the follow-up members on the right side or the left side for one broadcast band at the non-push-in (non-sliding) position of the actuating members. The slidable gate has switching fingers for pivotally moving the toggle levers, said switching fingers corresponding in number to said toggle levers. Upon shifting the slidable gate to the right (viewing the tuner from the front), the respective switching fingers engage the toggle levers with the follow-up members on the right side, and, upon shifting the slidable gate to the left, the respective switching fingers are engaged with the follow-up members on the left side. This "engagement" is achieved by the respective end portions of the toggle levers being inserted in the slots for receiving the follow-up members on the right side or the left side respectively. If, in the state of the actuating member thus having been engaged with the follow-up member on the right side or the left side for either of the broadcast bands, any optional one actuating member slides so as to be pushed in for station-selecting purposes, then the follow-up member which is engaged therewith also slides together, and, in accordance with the position where the cam of said follow-up member has been set, the tuning mechanism sets a specific state of tuning.
The Stamm patent, in view of the Newman patent wherein, in the tuner thereof, since there was no means to forcibly engage a toggle lever with a follow-up member while sliding one actuating member and maintain such engagement, though this engagement would not be released during the sliding of the follow-up member, there occurred shifting of the position of the follow-up member, so that there was a likelihood that correct tuning could not be achieved, uses connecting parts having locating portions in place of the toggle levers of the Newman patent. The respective connecting parts are articulately mounted to the respective actuating members, and the respective locating portions of said connecting parts are received in the respective slots in the shift means which corresponds to the slidable gate of the Newman patent. During the sliding movement of the actuating member, the locating portion is compelled to move within the slot in the shift means, so that the locating portion or the connecting part is caused to follow a limited path defined by said slot. At one position of the shift means such that the shift means engages the connecting parts with the follow-up members on either side, a part of the respective connecting parts are inserted "tightly" into the notches in the respective follow-up members. This state of "tight" insertion can be maintained so long as, during the sliding of the actuating member, the connecting part which moves together with said actuating member moves the locating portion thereof along the limited slot path. This construction settles the problems in the tuner of the Newman patent, that is, the likelihood that, during the sliding of the actuating member, that is, at the time a given pushbutton is pushed in, the toggle lever of the actuating member will be released from the engagement with the actuating member and the likelihood that there will occur shifting of the position of the follow-up member so that the tuning cam thereof will establish a state of erroneous tuning.
In the apparatus of the Stamm patent, since in manually shifting the shift means for broadcast band setting, it is necessary to engage the connecting parts "tightly" with the follow-up members for the selected broadcast band, and so the aid of some means is required for establishing such state of "tight" engagement. This means is a projection on the bottom of each connecting part which provides a resilient detect action. Once this state of "tight" engagement is established, it follows that it can be maintained so long as the locating portion of the connecting part passes the limited path within the slot in the shift means, during the sliding movement of the actuating member.
However while a given pushbutton is depressed one actuating member slides together with one selected follow-up member, and the shift means freely moves in the direction of its shifting movement. Such movement of the shift means during the sliding movement of the actuating member prevents the desired "tight" engagement of the associated connecting part and causes shifting in position of the sliding follow-up member which sometimes causes erroneous tuning. Also, there occurs the case, too, where the movement of the shift means during the sliding of the follow-up member causes the connecting part to come out of the notch in the follow-up member, in which case said follow-up member returns to its original non-slide position due to a resilient action. Accordingly, it is necessary to avoid the above-mentioned problems of the tuner of the Stamm patent.